Palmer Amaranth

Is glyphosate-resistant Palmer amaranth a growing challenge? View field demonstrations and hear from experts at the Glyphosate-Resistant Palmer Amaranth Management Field Day Wednesday, July 11 at Carleton.

Palmer amaranth has not been confirmed in conservation plantings in Nebraska; however, the identification and occurrence of Palmer amaranth in CRP fields in Iowa has raised concerns among weed scientists and growers about its spread into conservation plantings in Nebraska and offer some suggestions for growers.

Figure 1. A female glyphosate-resistant Palmer amaranth plant in a soybean field in south-central Nebraska. This plant has the capacity to produce up to half a million seeds. (All photos by Parminder Chahal)

Figure 1. Common pigweed species found in the Nebraska Panhandle. Palmer amaranth and waterhemp are ALS-resistant. Images, from top to bottom in each column, are of seed, seedlings, and plants in the vegetative growth stage. (Source Nebraska Extension EC94-138)

Palmer amaranth and waterhemp in the Panhandle are resistant to ALS-inhibiting herbicides. While control of these weeds in dry bean can be challenging, corn, irrigated small grains, and sugarbeet make good rotation options for control. A combined pre/post treatment strategy controls weeds in the early part of the season when crop yield is most impacted and weed species are most susceptible to control inputs.

Figure 1. (L) Palmer amaranth in corn and (R) a Palmer amaranth seedling. A member of the pigweed family, Palmer amaranth is a difficult to control broadleaf made even more difficult by its growing resistance to herbicides, including atrazine and HPPD inhibitors.